Plants adapted to arid zones such as a desert are known to have excellent ability to elongate their roots, so as to reach a water vein deep under the ground in order to avoid drought stress. By introducing a gene related to this ability into a general crop, it is expected that a root of the plant is promoted to efficiently absorb soil moisture and/or nutrient sources, and whereby the plant achieves improved drought stress resistance and an increased yield. Further, since the root also involves supporting the plant body, development of the root is an important factor for improvement of productivity of the plant.
For this reason, researches on a gene regulating elongation of a plant's root have been conventionally conducted. For example, Patent Literature 1 describes a technique for (i) obtaining, by the T-DNA tagging technique, a mutant in which root elongation is outstandingly suppressed as compared with a wild strain and (ii) using a gene or the like relating to such a phenotype. Further, Non-Patent Literature 1 describes one example of overexpression of Cyclin gene, as an example of root elongation promotion by a gene introduction technique. Non-Patent Literature 2 reports that an Arabidopsis thaliana AtCOL3 gene knockout plant has a phenotype in which a lateral root elongation is suppressed.